1. Technical Field of the Invention
The present invention relates to a temperature/voltage detecting unit for detecting a temperature and a terminal voltage of each of batteries of a heavy electric system for supplying a voltage to a motor for operating an electric car.
Further, the present invention relates to a battery element unit having a battery element and a temperature/voltage detecting unit corresponding to this battery element.
2. Description of Prior Art
Conventionally, electric cars are run by rotationally driving a motor which is supplied with a voltage from a battery of a heavy electric system. Recently, along with the progress of development of batteries with high performance of charge and discharge functions, there has been an increasingly strong demand for voltage management and temperature management of these batteries. For example, a heavy electric system battery for a driving system is structured by about twenty to thirty battery elements connected in series, and it has become necessary to manage both voltage and temperature of each of these battery elements. Therefore, a voltage detector and a temperature detector are necessary by the number of these battery elements.
As a conventional voltage detector, there has been used a voltage detector to which a zero magnetic flux method is applied as shown in FIG. 1. A voltage detector 101 shown in FIG. 1 has a magnetic core 103 which is wound up with a primary winding 105 and a secondary winding 107. The primary winding 105 is connected with a heavy electric system battery 111 structured by a plurality of power supplies 111a, 111b, . . . , and 111n connected in series, through a resistor 109. A Hall element 115 is provided in a gap 113 formed on a magnetic core 103.
In this case, a magnetic flux.PHI..sub.1 is generated within the magnetic core 103 by the primary current I.sub.1 flowing through the primary winding 105, and the Hall element 115 for detecting this magnetic field generates a voltage corresponding to a direction of the magnetic field and a size of the magnetic field, and outputs this voltage to a current amplifier 117. The current amplifier 117 amplifies a current based on the voltage from the Hall element 115 and flows an output current I.sub.2 to the secondary winding 107. When the output current I.sub.2 flows to the secondary winding 107, a magnetic flux.PHI..sub.2 is generated. In this case, the magnetic flux.PHI..sub.2 works to cancel the magnetic flux.PHI..sub.1.
When the magnetic flux.PHI..sub.2 becomes equal to the magnetic flux.PHI..sub.1, the magnetic flux.PHI..sub.1 within the magnetic core 103 becomes zero. Accordingly, the Hall element 115 makes the output zero, and the magnetic flux.PHI..sub.2 also becomes zero. In this state, the magnetic flux.PHI..sub.1 is generated again within the magnetic core 103 and an output is generated in the Hall element 115 as well, so that the magnetic flux.PHI..sub.2 becomes larger than the magnetic flux.PHI..sub.1 within the magnetic core 103. This operation is repeated in high frequency, and the output current I.sub.2 is made as an effective value. At this time, the following law of equal ampere-turns is established. EQU N.sub.1.multidot.I.sub.1 =N.sub.2.multidot.I.sub.2.
When the output current I.sub.2 from the current amplifier 117 is measured by using this expression, the primary current I.sub.1 can be obtained. A detection voltage across both ends of the resistor 119 becomes a voltage proportional to the output current I.sub.2.
However, according to the prior-art technique, a unit having a voltage detector and a unit having a temperature detector are provided separately for each battery element, and therefore, a battery unit as a whole has a large size for these detectors and a considerably large space has been necessary for these detectors.
Further, although the prior-art voltage detector has high precision, this has required a large size for the. magnetic core 103, the primary winding 105 and the secondary winding 107, resulting in a high cost as well.